Planetary gear sets of the aforementioned type are often used in automatic transmissions, which comprise planetary gear sets and are shifted by means of friction or shift elements, such as clutches and brakes and are typically connected to a start-up element subject to a slip effect and provided with a lock-up clutch, such as a hydrodynamic torque converter or a fluid coupling.
Thereby, certain planetary gear set couplings have proved to be advantageous for various reasons. For example, so-called “Simpson planetary gear sets,” with which a planetary carrier of a planetary gear set is connected to the ring gear of another planetary gear set and their two sun gears, have proved to be advantageous based on the low component load. In addition, Ravigneaux planetary gear sets are often used, with which two planetary gear sets are combined or reduced to a planetary gear set with a common bar and a common ring gear. This arrangement has the advantage that the number of required components is kept low. In addition, based on their high number of achievable gears with good gradation and their low construction costs, Lepelletier planetary gear sets are often used, which consist of one simple upstream planetary gear set and one main gear set formed from two dual-coupled individual planetary gear sets; thereby, the main planetary gear set is usually designed in the form of Ravigneaux planetary gear set, based on its binding ability.
However, in a disadvantageous manner, combinations of certain planetary gear set couplings are not realizable, based on their lack of binding ability. For example, a main gear set designed as a Simpson planetary gear cannot be easily integrated into a Lepelletier gear set.
In order to establish binding ability, within the framework of US 2010/0125017 A1, a planetary gear set with a sun gear designed in split form is proposed, by which a connection of the bar of the planetary gear set, viewed radially, inwards between the two components of the split sun gear to a shift element is enabled. In addition, within the framework of US 2010/0125017 A1, for the extension of the binding ability of elements of a transmission in planetary design, it is proposed to design in split form a ring gear of a planetary gear set perpendicular to its axis of rotation. Thereby, a brake is connected to the planetary carrier of the planetary gear set, by which the mounting of the two ring gear parts and the intermediate penetration part required for the brake is possible only from the opposite side. A ring gear designed in split form is described within the framework of GB 2429248A. Thereby, the ring gear parts designed in split form and the sun gears designed in split form are in operative connection with each other through at least one planetary gear that is designed to be long when viewed axially.
A ring gear with internal toothing is known from US2012/225748 which is split into at least two parts that are movable relative to one another, which are mounted on a common carrier element.
In addition, a split ring gear arises from CN201772042, wherein its two parts are connectable to each other by means of a connecting disk.
A ring gear of a planetary gear set designed as a sintered component arises from US 2003/017905 A, which consists of two off-tool halves, which, without subsequent shape-cutting, are assembled free of backlash after the insertion of moving jacks, whereas the halves of the ring gear are aligned with each other in such a manner that they are mutually supported by means of radial guides and torsional stops. Thereby, the halves of the ring gear are not axially fixed with each other, and, in their mounted state, are fixed by planetary gear carriers and one control part.
In addition, a ring gear of a planetary gear set is known from DE 4216402 A1, which is formed from two ring gear parts that, viewed axially, are arranged next to each other, each of which is provided with tooth bevels directed opposite to each other, whereas the two ring gear parts are welded together.
In automatic transmissions comprising planetary gear sets, it is known from the state of the art that the planetary carriers of planetary gear sets are, based on their relatively high mass, to be centered by slide bearings or radial needle roller bearings, while the sun gears or ring gears are in turn centered on the planetary carrier through the planetary gears.
Due to the typically used helical toothed running gears, axial forces arise on the sun gears and ring gears of planetary gear sets, while, in principle, the planetary carriers remain free of axial forces. Thereby, as a general rule, axial forces are derived on the sun gears or ring gears directly by means of, for example, axial needle bearings or grooved ball bearings or indirectly by means of coupled components, such as planetary carriers or additional sun gears or ring gears, in the housing or in its housing cover.